Squashed commit of the following:

commit fa229f7
Merge: eaab3c6 c3e3499
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 20:33:06 2021 -0700

    Merge branch 'develop' into mypy (and fixed types)

commit eaab3c6
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 20:00:45 2021 -0700

    reformat all multi-line function defs to one-arg-per-line

commit 3fe2b69
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 15:58:48 2021 -0700

    ccitt nit -- avoid casting needlessly

commit 15983d8
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 15:58:36 2021 -0700

    tweak CHANGELOG

commit 13dc0ba
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 15:43:46 2021 -0700

    add failing tests for dumppdf crash

commit 6b509c5
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 15:24:23 2021 -0700

    ccitt: apply misc PR feedback

commit feb031b
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 15:18:26 2021 -0700

    add missing None return type to all __init__ methods

commit c0d62d6
Author: Andrew Baumann <ab@ab.id.au>
Date:   Mon Sep 6 15:13:08 2021 -0700

    minor cleanup, remove a few more Any types

commit b52a059
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sun Sep 5 22:37:28 2021 -0700

    tighten up types, avoid Any in favour of explicit casts

commit e58fd48
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sun Sep 5 14:10:49 2021 -0700

    annotate ccitt.py, and fix one definite bug (array.tostring was renamed tobytes)

commit 6052906
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sat Sep 4 22:37:38 2021 -0700

    python 3.7 back-compat

commit 4dbcf87
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sat Sep 4 22:32:43 2021 -0700

    annotate pdfminer.jbig2

commit 0d40b7c
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sat Sep 4 22:31:33 2021 -0700

    annotate pdf2txt.py

commit 5f82eb4
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sat Sep 4 09:16:31 2021 -0700

    cleanup: make Plane generic

commit 624fc92
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 23:16:51 2021 -0700

    bluntly ignore calls to cryptography.hazmat

commit 96b2043
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 23:01:06 2021 -0700

    finish annotating, and disallow_untyped_defs for pdfminer.* _except_ ccitt and jbig2

commit 0ab5863
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 21:51:56 2021 -0700

    annotate pdffont

commit 4b689f1
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 18:30:02 2021 -0700

    annotate a couple more scripts; document sketchy code

commit 291981f
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 15:02:01 2021 -0700

    pacify flake8

commit 45d2ce9
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 14:31:48 2021 -0700

    annotate dumppdf, and comment likely bugs

commit 7278d83
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 13:49:58 2021 -0700

    enable mypy on tests and tools, fix one implicit reexport bug

commit 4a83166
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 13:25:59 2021 -0700

    pdfdocument: per dumppdf.py, get_dest accepts either bytes or str

commit 43701e1
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 13:25:00 2021 -0700

    layout: LAParams.boxes_flow may be None

commit 164f816
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 09:45:09 2021 -0700

    add whitespace, pacify flake8

commit 893b9fb
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 09:40:33 2021 -0700

    support old Python without typing.Protocol

commit dc24508
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Sep 3 09:12:03 2021 -0700

    Move "# type: ignore" comments to fix mypy on Python < 3.8

    The placement of these comments got more flexible in 3.8 due to
    python/mypy#1032

    Satisfying older Python and fitting in flake8's 79-character line
    limit was quite a challenge!

commit da03afe
Author: Andrew Baumann <ab@ab.id.au>
Date:   Thu Sep 2 22:59:58 2021 -0700

    fix text output from HTMLConverter

commit 5401276
Author: Andrew Baumann <ab@ab.id.au>
Date:   Thu Sep 2 22:40:22 2021 -0700

    annotate high_level.py and the immediately-reachable internal APIs (mostly converters)

commit cc49051
Author: Andrew Baumann <ab@ab.id.au>
Date:   Thu Sep 2 17:04:35 2021 -0700

     * expand and improve annotations in cmap, encryption/decompression and fonts
     * disallow untyped calls; this way, we have a core set of
       typed code that can grow over time
       (just not for ccitt, because there's a ton of work lurking there)
     * expand "typing: none" comments to suppress a specific error code

commit 92df54b
Author: Andrew Baumann <ab@ab.id.au>
Date:   Wed Sep 1 20:50:59 2021 -0700

    update CHANGELOG

commit f72aaea
Merge: ff787a9 8ea9f10
Author: Andrew Baumann <ab@ab.id.au>
Date:   Wed Sep 1 20:47:03 2021 -0700

    Merge branch 'develop' into mypy

commit ff787a9
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sat Aug 21 21:46:14 2021 -0700

    be more precise about types on ps/pdf stacks, remove most of the Any annotations

commit be15501
Author: Andrew Baumann <ab@ab.id.au>
Date:   Sat Aug 21 10:13:58 2021 -0700

    silence missing imports, (maybe?) hook to tox

commit ff4b6a9
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Aug 20 22:49:06 2021 -0700

    turn on more strict checks, and untangle the layout mess with generics

    Status:
    $ mypy pdfminer
    pdfminer/ccitt.py:565: error: Cannot find implementation or library stub for module named "pygame"
    pdfminer/ccitt.py:565: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
    pdfminer/pdfdocument.py:7: error: Skipping analyzing "cryptography.hazmat.backends": found module but no type hints or library stubs
    pdfminer/pdfdocument.py:8: error: Skipping analyzing "cryptography.hazmat.primitives.ciphers": found module but no type hints or library stubs
    pdfminer/pdfdevice.py:191: error: Argument 1 to "write" of "IO" has incompatible type "str"; expected "bytes"
    pdfminer/image.py:84: error: Cannot find implementation or library stub for module named "PIL"
    Found 5 errors in 4 files (checked 27 source files)

    pdfdevice.py:191 appears to be a real bug

commit 5c9c0b1
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Aug 20 17:22:41 2021 -0700

    finish annotating layout

commit 0e6871c
Author: Andrew Baumann <ab@ab.id.au>
Date:   Fri Aug 20 16:54:46 2021 -0700

    general progress on annotations
     * finish utils
     * annotate more of pdfinterp, pdfdevice
     * document reason for # type: ignore comments
     * fix cyclic imports
     * satisfy flake8

commit 17d59f4
Author: Andrew Baumann <ab@ab.id.au>
Date:   Thu Aug 19 21:38:50 2021 -0700

    WIP on type annotations

    With the possible exception of psparser.py, this is far from complete.

    $ mypy pdfminer
    pdfminer/ccitt.py:565: error: Cannot find implementation or library stub for module named "pygame"
    pdfminer/ccitt.py:565: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
    pdfminer/pdfdocument.py:7: error: Skipping analyzing "cryptography.hazmat.backends": found module but no type hints or library stubs
    pdfminer/pdfdocument.py:8: error: Skipping analyzing "cryptography.hazmat.primitives.ciphers": found module but no type hints or library stubs
    pdfminer/image.py:84: error: Cannot find implementation or library stub for module named "PIL"